1. Field of the Invention
The present invention relates generally to an apparatus and method for mobile broadcasting services in a digital video broadcasting system, and more particularly to an apparatus and method for providing signaling information using inband transmission in a digital video broadcasting system.
2. Description of the Related Art
Generally, a digital broadcasting system is a broadcasting system that uses a digital transmission technology providing services such as Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Digital Multimedia Broadcasting (DMB), and the like.
The DVB system providing DVB service is a European digital broadcasting technology and transmission standard for supporting not only existing digital broadcasting but also digital multimedia service to a mobile or portable device.
The DVB system can multiplex broadcasting data based on MPEG 2 Transport Stream (TS), and simultaneously transmit data streams based on Internet Protocol (IP). Also, the DVB system can multiplex data streams according to diverse broadcasting services into one IP stream and transmit the IP stream where a user terminal demultiplexes the received IP stream into data streams according to individual services. The user terminal demodulates the data streams according to individual services, and outputs the demodulated data to a screen, thus, requiring information on what kind of diverse services are provided from the DVB system, what content the respective services include, and the like.
FIG. 1 illustrates a frame (T2 frame) structure of a physical layer in a general 2nd generation terrestrial DVB broadcasting system (“DVB-T2 system”).
The frame structure illustrated in FIG. 1 may be simply divided into a P1 and P2 symbol part (“preamble field”) and a data symbol part (“data field”). In the preamble field, signaling information of frames is transmitted, and in the data filed, data, that is, payload, is transmitted.
First, the P1 preamble that is transmitted in the P1 symbol part of the preamble field is used to scan an initial signal of a frame in a receiver. Also, the P1 preamble is used to detect a frequency offset and to tune a center frequency in the receiver. Also, the P1 preamble is used to transmit identification information of a frame, a Fast Fourier Transform (FFT) size, and other transmission information to the receiver.
The P1 preamble is transmitted at the start of the frame, and is composed of a three-bit S1 field and a four-bit S2 field. The S1 field includes information on configurable elements (SISO, MISO, or mixed system) of the DVB-T2 system. Also, the S2 field includes information on the FFT size of the DVB-T2 system and a guard interval size.
Next, the P2 symbol part of the preamble field is used to transmit L1 signaling information. Here, the L1 signaling information includes information on DVB-T2 system parameters and data field configurable elements. Also, the P2 symbol part is composed of an L1-pre-signaling field and an L1-post-signaling field. The L1-pre-signaling field has a fixed length of 200 bits, and the L1-post-signaling field has a variable length.
In the L1-pre-signaling field, information as shown in Table 1 below is transmitted.
TABLE 1TYPE 8 bitsBWT_EXT 1 bitS1 3 bitsS2 4 bitsL1_REPETITION_FRAG 1 bitGUARD_INTERVAL 3 bitsPAPR 4 bitsL1_MOD 4 bitsL1_COD 2 bitsL1_FEC_TYPE 2 bitsL1_POST_SIZE18 bitsL1_POST_INFO_SIZE18 bitsPILOT_PATTERN 4 bitsTX_ID_AVAILABILITY 8 bitsCELL_ID16 bitsNETWORK_ID16 bitsT2_SYSTEM_ID16 bitsNUM_T2_FRAMES 8 bitsNUM_DATA_SYMBOLS12 bitsREGEN_FLAG 3 bitsL1_POST_EXTENSION 1 bitNUM_RF 3 bitsCURRENT_RF_IDX 3 bitsT2_VERSION 4 bitsRESERVED 6 bitsCRC_3232 bits
Information that is transmitted in the L1-pre-signaling field is described in detail in the DVB-T2 standard (ETSI EN 302 755).
Using L1_post_size (18 bits) information among the information transmitted in the L1-pre-signaling field, a start position of the data field can be calculated. The size of the L1-pre-signaling field is fixed to 200 bits. Accordingly, by adding the L1_post_size to the size of the L1-pre-signaling field, the start position of the data field can be known. That is, if the L1_post_size information is known, the start position of the data field that is positioned next to the L1-post-signaling field can be known.
The L1-post-signaling field includes a configurable field, a dynamic field, and an extension field. In addition, the L1-post-signaling field includes a Cyclic Redundancy Check (CRC) field for confirming existence/nonexistence of errors in the three fields, and a padding part that is filled with a parity part.
The size of the L1-post-signaling field can be confirmed by the L1_post_size of the L1-pre-signaling field. Accordingly, the receiver receives the L1-post-signaling field after receiving the L1-pre-signaling field.
Last, the data field can construct various services based on a Physical Layer Pipe (PLP) as mentioned in the DVB-T2 standard. Accordingly, the user terminal finds the PLP allocated to the user terminal itself from the PLP based data field that constitutes the services, and receives desired information.
Lately, with the increase of user demands for mobile broadcasting services, diverse broadcasting systems have been proposed. For example, Multimedia Broadcast and Multicast Services (MBMS) using mobile communication networks, Terrestrial-Digital Multimedia Broadcasting (T-DMB) for portable terminals, mediaFLO, DVB Handheld (DVB-H), and the like, have been proposed.
In addition, research for mobile broadcasting services using the DVB-T2 system has been made. However, because the DVB-T2 system is designed for terrestrial services, its performance deteriorates in a mobile environment.
Accordingly, in order to support the mobile services using the DVB-T2 system, the signaling and data robustness problems in the mobile environment need to be resolved. Specifically, P2 symbols that are used in the DVB-T2 system are transmitted for a short period through one (32K, 16K FFT), two (8K FFT), four (2K FFT), or 16 (1K FFT) OFDM symbols in accordance with the size of the FFT. Accordingly, in comparison to the data field that is transmitted through a relatively large number of symbols (255 OFDM symbols at maximum), such a data field is vulnerable in that it has relatively small time diversity.